Narrow disperse (meth)acrylate polymers having a small Mw/Mn have been presented as viscosity index improvers which are added to improve the fuel saving performance of lubricating oils used in devices such as automobile engines and other internal combustion engines, transmissions, and the like (see, for example, Patent Literatures 1 to 3).
Such narrow disperse (meth)acrylate polymers are produced by, for example, atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain-transfer polymerization (RAFT), nitroxide-mediated polymerization (NMP), boron-mediated polymerization and catalytic chain transfer (CCT) polymerization (see, for example, Patent Literatures 4 to 6). Another useful production method is anionic polymerization (typically, highly living anionic polymerization) (see, for example, Patent Literature 7). While narrow disperse (meth)acrylate polymers can be obtained by these production methods, there have been demands for (meth)acrylate polymers which can impart high shear viscosity stability to lubricating oils.